The present invention relates to a device and a method for detecting the position of one element relative to another element, in particular for detecting the position of a rotor relative to a stator.
More particularly, in some embodiments, the invention relates to a device for dispensing a liquid in doses, in particular in the area of medicine, e.g., an infusion or injection apparatus, wherein the set dosage of the dispensed liquid or liquid to be dispensed can be ascertained by the position of a rotor, such as a threaded rod, relative to a stator, such as a casing, device body, or portion of an injection device, including those known as injection “pens”. In general, a dosage to be dispensed by a pen is set by turning for example a dosing button and dispensed by then pressing the dosing button.
In order to dose a liquid—for example insulin, hormone preparations or the like—to be dispensed from a medical injection instrument or device as exactly as possible, it is necessary to be able to monitor the process of setting a dosage, in order—for example, in the event of an incorrect dosage—to output a warning signal or to prevent the dosage from being dispensed. Since the dosage is usually set by turning a rotor situated in a casing of device pen, the rotor generally being provided with a thread, the advance of the rotor can be ascertained from the turns made in order to set the dosage, and a dosage to be dispensed or a dispensed dosage thus determined.
Known devices for measuring this turning movement are based on mechanical principles and are therefore costly and relatively imprecise.